Call of duty series: question

Hi
I'm playing COD 1 & United offensive. The problem is in both game almost in every levels the game stops to continue, I mean its running but not going to next level or objective is not updating even if I do it as it says. Therefore I've to repeat the same level or objective over & over again just to make the game continue. I think the script is not well designed so if I don't follow the exact way it stops continuing. & its hard to know what is the exact way to do a objective. Another prob is some of the characters stop moving & stand like statue unless I go to them & use the action key to animate them again. its really very annoying to repeat the same thing again & again. Its just spoiling the game! any one has any solution for this?